1. Field of the Invention
The present invention relates to a keyboard apparatus ideally used for a personal computer of a notebook type or the like for which thinness is required.
2. Description of the Related Art
A conventional keyboard apparatus will be described in conjunction with the accompanying drawings. FIG. 6 is a partial sectional view of the conventional keyboard apparatus, and FIG. 7 is a sectional view taken at the line 7--7 of FIG. 6. FIG. 8 is a schematic representation of a supporting substrate used for the conventional keyboard apparatus, wherein FIG. 8A is a partial top plan view of the supporting substrate, and FIG. 8B is a sectional view taken at the line 8B--8B of FIG. 8A.
A plate-like supporting substrate 51 made of a metal has: a pair of rectangular slits 51a and two pairs of rectangular slits 51b provided in parallel; a first retaining portion 51c which is positioned between the paired slits 51a, provided by cutting and raising a square wall so that it protrudes upward, and has a trapezoidal section; two second retaining portions 51d, each of which is positioned between the slits 51b of each pair, provided by cutting raising square walls so that they protrude upward, and have U-shaped sections; and vertical through holes 51e formed by providing the slits 51a and 51b, the first retaining portion 51c, and the second retaining portions 51d.
The single first retaining portion 51c and the two second retaining portions 51d are disposed triangularly on the supporting substrate 51. A plurality of sets, each set consisting of the three retaining portions, are formed on the supporting substrate 51.
A contact sheet 52 composed of two layers of flexible resinous films (not shown) has printed contacts on two opposing surfaces of the resinous films disposed with a predetermined gap provided therebetween. The sheet 52 has a plurality of apertures 52a. The first retaining portion 51c and the second retaining portions 51d are mounted on the supporting substrate 51, being inserted in the respective apertures 52a.
A link assembly L formed of a synthetic resin is constituted by a first supporting member 53 and a second supporting member 54. The first supporting member 53 is composed of: a plate-like base 53a; a round aperture 53b provided at the center of the base 53a; pivot shafts 53c installed on both sides at the center of the base 53a; a rotary shaft 53d which is provided about the pivot shafts 53c and which projects from the sidewall of one end of the base 53a; a pair of arms 53e which are provided around the pivot shaft 53c, coupled to the base 53a on the opposite side thereof, and protrude in parallel to each other; and slide retaining pins 53f provided so that they protrude inward with respect to the ends of the arms 53e.
The second supporting member 54 is constituted by a base 54a, a pair of arms 54b which are formed approximately in a U shape by being coupled to the base 54a and which are provided in parallel to each other, a slide pin 54c provided in such a manner that it protrudes outward on the free end of each of the arms 54b; a pair of pivot apertures 54d provided at the middle of each of the arms 54b such that they face each other; and a T-shaped rotary retaining pin 54e which is coupled to the base 54a and extends in the opposite direction from the arms 54b.
The first supporting member 53 and the second supporting member 54 are connected by the pivot shafts 53c that are fitted from inside into the pivot apertures 54d so that they intersect with each other. The slide retaining pin 53f is slidably retained in the single first retaining portion 51c, and the rotary retaining pin 54e is rotatably retained and held in the two second retaining portions 51d, thus configuring a set retaining portions of the link assembly L.
A key top 55 composed of a molding made of a synthetic resin has supporting portions 55a and 55b on the bottom surface thereof. The rotary shaft 53d of the first supporting member 53 and the slide pin 54c of the second supporting member 54 are retained by the supporting portions 55a and 55b, respectively.
A rubber spring 56 formed of a rubber constituent is constructed of a dome portion 56a that has a section shaped like an inverted U and a flat top surface, a cylindrical contact portion 56b provided on the top of the dome portion 56a, and a protuberance 56c provided so that it protrudes downward in the dome portion 56a. The bottom of the dome portion 56a of the rubber spring 56 is fixed onto the sheet 52 by an appropriate means, and the dome portion 56a is inserted in the round aperture 53b of the first supporting member 53 so that the contact portion 56b comes in contact with the bottom surface of the key top 55. The springiness of the dome portion 56a urges the link assembly L and the key top 55 upward at all times. At this time, the protuberance 56c provided on the dome portion 56a is positioned above the sheet 52.
A plurality of the link assemblies L, the key tops 55, the rubber springs 56 configured as discussed above are arranged on the supporting substrate 51 and the sheet 52 to make up the keyboard apparatus. This keyboard apparatus is installed on a personal computer or the like. In using the personal computer, when the key top 55 is pressed downward against the springiness of the rubber spring 56, the link assembly L moves down with the intersecting point as its center. At this time, the slide retaining pin 53f slides in the first retaining portion 51c, while the slide pin 54c slides in the supporting portion 55b, causing the link assembly L to be collapsed. This squeezes and deforms the dome portion 56a, causing the protuberance 56c to push the contact sheet 52. The pushing force turns ON the contact provided on the sheet 52, so that the input signal of the key is transmitted to a control member (not shown) of the personal computer or the like. The moment the key top 55 is released, the deformed dome portion 56a resets itself by its own springiness, the link assembly L and the key top 55 accordingly restore their original conditions, and the contact of the sheet 52 turns OFF. In this way, the contact is turned ON/OFF.
In the process for assembling the conventional keyboard apparatus described above, to dispose the slide retaining pin 53f such that it is held by the first retaining portion 51c, the arms 53e of the first supporting member 53 are flexibly spread outward to insert them into the first retaining portion 51c to hold them therein. Similarly, in order to dispose the rotary retaining pin 54e so that it is held in the second retaining portion 51d, the arms 54b of the second supporting members 54 are flexed inward to insert them into the second retaining portions 51d to hold them therein.
The first retaining portion 51c, however, has the following disadvantage because of its square shape. In the assembly process of the conventional keyboard apparatus, the two arms 53e provided with the slide retaining pins 53f have to be flexed to insert them into the first retaining portion 51c as described above, resulting in poor assemblability.
Further, the slits 51a and 51b are formed in the supporting substrate 51, then the wall between the slits are cut and raised to form the first retaining portion 51c and the second retaining portions 51d. As a result, the through holes 51e are formed in the supporting substrate 51 as mentioned above. Dust intrudes into the keyboard apparatus from the back face of the supporting substrate 51, adversely affecting the operation or the like of the link assembly L.